1. Field of the Invention
The present invention relates generally to an oil filter for vehicles and, more particularly, to an end-cap structure of an oil filter for vehicles which is designed such that thermal deformation of the end-cap can be minimized when the filter is manufactured, and reliable sealing can be maintained.
2. Description of the Related Art
As is well known to those skilled in this art, engines for vehicles include sliding parts such as a cylinder and a piston and rotating parts such as a crank and a cam. When the engine is operated, moving parts generate a lot of frictional heat. If the state of being heated by frictional heat is continuous, abrasion damage is caused, whereby vehicle driving may become impossible. To prevent this problem, engines are provided with a lubricating device which supplies an appropriate amount of oil to the moving parts of an engine.
An oil filter for vehicles filters oil to be supplied to the moving parts of the engine so that as clean oil as possible can be supplied to the moving parts.
Referring to FIGS. 1 and 2, a conventional oil filter 1 includes a filter media 2 which defines a passage 3 in a central portion thereof, and upper and lower end-caps 4 and 5 which are respectively attached to upper and lower ends of the filter media 2. In detail, the upper end-cap 4 is made of plastic. A hole 6 is formed in a central portion of the upper end-cap 4, and a flange ring 7 protrudes downwards from a portion of the upper end-cap 4 that defines the hole 6.
The oil filter 1 is manufactured in such a way that the upper and lower end-caps 4 and 5 are formed using plastic, inner surfaces of the upper and lower end-caps 4 and 5 that face each other are melted by heat, and then the opposite ends of the filter media 2 are respectively pressed onto the melted surfaces of the upper and lower end-caps 4 and 5. For example, oil filters which have the above-mentioned structure and are manufactured by the above-mentioned method were proposed in Korean Utility Model Registration No. 325385, No. 378939 and No. 423005 and Korean Patent Laid-open Publication No. 2006-75618.
The oil filter 1 manufactured by the above-mentioned method is installed in an oil housing. A housing core is inserted into the passage 3. Reference numeral 8 denotes an elastic plunger of a bypass or relief valve which is provided on an upper end of the core. The end of the flange ring 7 and the valve plunger 8 make contact with each other, thus sealing the hole 6 of the end-cap 4. Referring to the arrow {circle around (1)} of FIG. 1, in this state, oil passes through the filter media 2 and flows through the passage 3 before being supplied to the engine, and the oil circulates along this path.
The filter media functions to filter oil, but the efficiency thereof is reduced in proportion to the degree of contamination of the oil and the period of use thereof. At last, the filter media 2 may be clogged so that it is impossible for oil to pass through the filter media 2. In this case, supply of oil to the engine is completely interrupted, thereby causing loss of lubricant and cooling functions. As a result, the engine may break down. To prevent this problem, when the filter media 2 is clogged, the plunger of the bypass valve is operated.
In detail, when the filter media 2 is clogged, a pressure difference between the inside and the outside of the oil filter occurs. The plunger 8 is moved by the pressure difference in a direction in which a sealing state formed by contact between the ring 7 and the plunger 8 is released. Thereby, the bypass valve and the hole 6 open. Referring to the arrow {circle around (2)} of FIG. 1, in this state, oil passes through the hole 6 of the end-cap 4 without passing through the filter media 2 and then is supplied to the engine via the passage 3, and the oil circulates along this path.
In this case, there is high probability of the oil that is supplied to the engine through this path is very contaminated. Therefore, so long as the filter media 2 is normally operated, the end of the flange ring 7 and the surface of the valve plunger 8 must be maintained as close as possible in order to prevent oil that is not filtered from being directly supplied to the engine.
However:
1) in a manufacturing process, when the inner surface of the end-cap 4 is melted, the end of the ring 7 is easily deformed or damaged by heat. As a result, there is difficulty maintaining the close contact between the end of the ring 7 and the surface of the valve plunger 8.
2) since such deformation irregularly occurs on each end-cap 4, full inspection for associated sealing portions must be conducted every time an end-cap is manufactured. Depending on the degree of deformation, whether the manufactured end-cap is defective or not is determined. In other words, even in the full inspection of the end-cap 4, some deformation or damage must be allowed.
3) Consequentially, this means that some contaminated oil may be directly supplied to the engine through the hole 6 of the end-cap 4 despite the filtering function of the oil filter 1 being normal.
4) Furthermore, even when only the end of the ring 7 is damaged, the entirety of the end-cap 4 must be discarded, thus reducing economic efficiency.